{
  "schema_version": "1.3.0",
  "slug": "how-must-an-instance-handle-partial-failure-during-cross-region-replication",
  "title": "How must an instance handle partial failure during cross-region replication?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** Replication spans multiple regions, partial failures are possible, and reads can be served from multiple regions. * **Does not apply when:** Replication is atomic across all regions (single-transaction multi-region commi",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-must-an-instance-handle-partial-failure-during-cross-region-replication.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-must-an-instance-handle-partial-failure-during-cross-region-replication.py",
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  "remnant_summary": {
    "core_distinction": "The separation between **source commit** (the source region has durably written the state) and **replica convergence** (all target regions have received and applied the state). Relying on source commit creates the **Replication Split Vision**: the source believes the operation is complete, some targets have the data, others do not, and reads from different r...",
    "what_was_observed": "In multi-region agent architectures, failing to handle partial replication produces three primary failure modes: 1. **Region-Dependent Reads:** A user queries the system in the US (where replication succeeded) and sees data X. The same user queries in EU (where replication failed) and sees stale data Y. Both queries appear successful. 2. **Split-Brain Writes:** A target region that failed to receive the update then w...",
    "condition_of_validity": "* **Applies when:** Replication spans multiple regions, partial failures are possible, and reads can be served from multiple regions. * **Does not apply when:** Replication is atomic across all regions (single-transaction multi-region commit), or reads are always routed to the source region.",
    "decision_boundary": "1. **Was the source write durably committed?** If no, standard retry applies. If yes, proceed. 2. **Do all target regions acknowledge the write?** If yes, replication is complete. If no, partial failure has occurred. 3. **Is the `read_routing_directive` updated to exclude failed regions?** If no, readers may see stale data from failed regions. The instance m...",
    "operational_effect": "1. **Read Consistency:** Prevents region-dependent read divergence by routing reads away from failed regions. 2. **Split-Brain Prevention:** Blocks writes to failed regions until they re-synchronize with the source. 3. **Deterministic Recovery:** Provides the exact recovery predicate, so successors can reconcile without manual intervention."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
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    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "12a46b16d1e62a1ca4a9a4e548bce86d67458635edfab7b45e7f05ff45af6436",
    "verified_classes": [
      "ReplicationVerdict",
      "TargetAck",
      "ReplicationState",
      "ReplicationPolicy",
      "ReplicationManifest",
      "CrossRegionReplicationGuard"
    ],
    "verified_functions": [
      "_hash",
      "evaluate_replication"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 0,
    "raised_exceptions": [],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib",
      "json"
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    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}